The invention relates to a collapsible fire fighting bucket for carrying with a helicopter for fighting forest fires, and in particular to an improved dump valve associated with the bucket.
Collapsible fire fighting buckets carried by helicopters have become standard equipment for fighting wild fires, and examples of such fire buckets are found in U.S. Pat. Nos. 4,474,245 and 4,576,287, both invented by Donald B. Arney. The patents disclose fire fighting buckets made of pliable fabric material having an open upper end with a rim to facilitate filing from an open body of water, a side wall extending downwardly from the rim, and a bottom cooperating with the side wall and having an opening. A tubular extension made of pliable material extends from an opening in the bottom to a free end formed with a discharge port to serve as a dump valve. The discharge port has an array of grommetted openings extending therearound to receive a plurality of cords so that the tubular extension can be drawn upwardly into the bucket by the cords before the bucket is filled with water. The discharge port has a circumferential sealing lip made of soft and resilient material, which forms two opposite lip portions which are brought into sealing engagement with each other to minimize water leakage from the tubular extension when the dump valve is positioned below the water surface in the bucket. The sealing lip has an array of unprotected openings extending therearound and in alignment with the grommetted openings in the port. The plurality of cords serve as purse lines and pass through the aligned openings to draw the sealing lips into engagement with each other when the cords are tightened. Tension in the cords supports the extension, and the extension is drawn upwardly through the bucket to be supported in a position which can be below an upper level of water within the bucket. Weight of water acting on the tubular extension tensions the cords further and ambient pressure of water acting on the sealing lips augments initial sealing generated by tension in the cords.
To dump the water the valve is opened by rapidly loosening the purse lines by a release or trip mechanism, which permits the tubular extension to fall quickly through the opening in the bottom of the bucket. The lip portions are opened essentially simultaneously under the weight of water, permitting rapid discharge of water with negligible obstruction.
The prior art bucket has been very reliable and, in general, requires little maintenance. However, one area of wear relates to the array of unprotected openings in the sealing lip portions which receive the cords or purse lines passing therethrough. It has been found that the relatively soft sealing material of the lips can wear rapidly after many deployments of the valve due to abrasion of the purse lines, and the wear results in loss of sealing effectiveness with a corresponding leakage of water through the dump valve.